In this section we combine our interests in the intercellular dialogues which control the emigratory, secretory and proliferative properties of monocytes. T cells and endothelial cells under in vitro conditions and in the complex milieu of tissue reactions. Employing delayed type skin reactions in man we wish to understand the structural and functional phenotypes of emigratory cells with monoclonal reagents and in situ hybridization probes. Employing recombinant lymphokines and monokines we wish to examine their selective roles in the cellularity of the delayed response and their influence on the process of emigration, the proliferative epidermal reactions and the turnover of Langerhans cells. Employing cultured endothelial cells (EC) we wish to define the selective binding properties of blood monocytes, the nature of the binding sites in the junctional complexes and the biochemical determinant which regulate the production of the arachidonate metabolites arising from the cyclooxygenase and lipoxygenase pathways. In particular, the unique priming effects of bacterial LPS for markedly enhanced secretion of vaso active metabolites. This and other subprojects of this proposal will be focussed on a new clinical and laboratory program to understand the basic immunological defects in patients with AIDS. Employing the facilities of the Hospital of The Rockefeller University we will examine the cellular tropisms of HTLV-III, defects in the endocytic and secretory repertoire of mononuclear phagocytes, factors controlling DTH reactions and the nature of Kaposi's sarcoma cells.